German-born writer Jakob Wassermann was a popular novelist in the first part of the 20th century. His novels often explored the theme of a nonconformist character encountering an uncaring society, or, more specifically, the issue of retaining Jewish heritage in the face of anti-Semitism and cultural assimilation. Consistently popular in his day, his intense, psychological analysis of modern society and religion sometimes became too abstract for general audiences.
From the description of Jakob Wassermann letters and papers, 1924-1931. (Pennsylvania State University Libraries). WorldCat record id: 51797899
Alma Mahler speaks of Wassermann several times in her memoir Mein Leben, including an anecdote about his advising Werfel on the manuscript of Werfel's novel Verdi. Marta Wassermann-Karlweis (née Karlweis; 1889-1965) was Jakob's second wife; they were apparently together as a couple since around 1919, and were married in 1926 (following Wassermann's divorce from his first wife in the same year). Nast appears to have been a previous acquaintance of Wassermann and an attorney; Wassermann had just recently received a letter from Nast.
From the description of Correspondence to Alma Mahler and Franz Werfel, 1923-1935. (University of Pennsylvania Library). WorldCat record id: 155864754